Silica Dust Hazards in Construction — Legal Requirements and Control Measures
TL;DR
Respirable crystalline silica (RCS) from cutting, drilling or grinding stone, concrete, brick and mortar is a known carcinogen. Prolonged exposure causes silicosis — an incurable, progressive lung disease. COSHH assessments and engineering controls are required for any task generating silica dust. RPE alone is not sufficient.
What is Silica Dust?
Silica is a natural mineral found in most rocks, sand and clay. When materials containing silica are cut, drilled, ground or crushed, fine particles are released. Particles small enough to reach the deep lung are called respirable crystalline silica (RCS).
Construction materials with high silica content include: concrete, mortar, natural stone, slate, some sandstones, and clay bricks.
Legal Framework
The Control of Substances Hazardous to Health Regulations 2002 (COSHH) require employers to:
- Assess the risk from hazardous substances including RCS
- Prevent or adequately control exposure
- Use controls in a specific hierarchy (not jump straight to RPE)
- Maintain controls and monitor effectiveness
- Carry out health surveillance where appropriate
The workplace exposure limit (WEL) for RCS is 0.1 mg/m³ (8-hour TWA). This is a very low level — impossible to achieve with RPE alone without engineering controls.
High-Risk Tasks in Construction
| Task | Risk Level |
|---|---|
| Dry cutting concrete or stone with angle grinder | Very high |
| Jackhammering concrete | Very high |
| Scabbling or surface preparation | High |
| Block and brick cutting (dry) | High |
| Drilling into concrete or masonry | Medium-High |
| Hand sanding or rubbing down renders | Medium |
| Wet cutting (with water suppression) | Lower |
Control Hierarchy
- Eliminate — avoid generating dust (pre-cut materials off-site, specify factory-made components)
- Substitute — use lower-silica materials where structural requirements allow
- Engineering controls (in priority order):
- Water suppression (on-tool water feeds for cutting and drilling)
- On-tool dust extraction (H-class vacuum connected to cutting tool)
- Local exhaust ventilation (LEV) for fixed operations
- Administrative — restrict time spent on high-exposure tasks; rotate workers; keep others away from work area
- RPE — FFP3 disposable masks or P3 half-face respirators where engineering controls alone cannot achieve the WEL
RPE Selection for Silica Dust
RPE must achieve a sufficient assigned protection factor (APF) for the exposure level:
| RPE Type | APF | Use For |
|---|---|---|
| FFP2 disposable | 10x | Lower exposure tasks with engineering controls |
| FFP3 disposable | 20x | Most cutting and grinding tasks |
| Half-face with P3 filter | 20x | Extended duration work |
| Powered air purifying (TH3 hood) | 20x | High-dust or hot environments |
RPE must fit-tested (for tight-fitting facepieces) and maintained. Disposable masks should be used once only.
Health Surveillance
Employers of workers regularly exposed to silica dust should implement health surveillance, typically annual lung function testing. Health surveillance records must be kept for 40 years.
COSHH Assessment Requirements
A COSHH assessment for silica-generating tasks must include:
- Identification of the silica-containing materials
- Description of the tasks generating dust
- Assessment of likely exposure levels
- Selected control measures in order of hierarchy
- RPE specification with maintenance requirements
- Emergency procedures
- Health surveillance arrangements
FAQs
How quickly does silicosis develop?
Silicosis can develop after many years of lower-level exposure (chronic silicosis) or within months from very high-level exposure (accelerated silicosis). Acute silicosis from extreme exposure is rare but can be rapidly fatal. There is no cure — only symptom management.
Is a simple dust mask enough for cutting concrete?
No. Standard dust masks (EN 149 FFP1 or FFP2) are insufficient for high-silica tasks without engineering controls. Engineering controls (water suppression, on-tool extraction) must be the primary measure. FFP3 or P3 RPE is then used as a supplementary control.
Does water suppression alone control silica dust adequately?
Water suppression significantly reduces dust, but is unlikely to achieve the WEL alone on very high-exposure tasks such as dry grinding of concrete surfaces. A combination of water suppression and RPE is typically required.
Do sub-contractors need their own COSHH assessments?
Yes. Each employer is responsible for their own COSHH assessments for the substances their workers are exposed to. The principal contractor may set site-wide rules for dust control, but individual contractors must comply with COSHH for their own scope.
What should be in the RAMS for silica-generating tasks?
The RAMS must reference the COSHH assessment, specify the engineering controls to be used, specify the RPE required, identify who is authorised to work on the task, and set out the supervision and monitoring arrangements.